In recent years, the increasing desire to reduce pollutants in work environments has prompted adhesives manufacturers to seek elimination of volatile solvents from adhesive compositions. Moreover, elimination of volatile solvents is desirable to reduce energy consumption, since considerable heat energy is required to evaporate volatile solvents when curing the adhesive compositions.
A number of radiation curable adhesive compositions have been developed which are essentially 100 percent reactive. Each component of the composition reacts to become incorporated into the cured adhesive upon exposure to radiation. Thus, the need to evaporate volatile solvents from the composition is eliminated.
A number of pressure sensitive adhesives have been disclosed in the art which are produced by exposing inherently tacky polymers to radiation, thereby increasing their adhesivity (see, e.g., "Radiation Curing of Pressure Sensitive Adhesives: A Literature Review", Stueben, K. C., Adhesives Age, June, 1977).
U.S. Pat. No. 3,661,618 discloses a method of producing a pressure sensitive adhesive which involves applying to a backing material a composition of 100 parts of a liquid alkyl acrylate, 0.01 to 10 parts of a crosslinking agent and from 1 to 50 parts of a polymer capable of increasing the viscosity of the liquid alkyl acrylate, and exposing the composition to high energy particle radiation. As is pointed out in that patent, at Col. 1, line 42 - Col. 2, line 9, the obtainment of pressure sensitive adhesives having good properties by irradiation techniques has proven a most difficult task to those in the art. In order to have substantial commercial utility, the composition, upon irradiation, most develop a reasonably good balance of adhesivity and cohesivity.
Despite the ingenuity displayed by the art, it is always desirable to develop new 100 percent reactive pressure ssnsitive adhesive compositions which display good adhesive properties in the cured state.